The Barcelona process is an ongoing process and its first economic results are still insignificant. This study had two objectives. The first is to provide a global assessment of its impacts on the three North African countries that have already became members of this process, namely Tunisia, Morocco and Egypt. The second objective is to explore its potentials by a larger inclusion of agriculture in the Euromed partnership. The approach adopted in this paper is the use of the MIRAGE global Computable General equilibrium Model and the MacMAPS database that gives a very detailed picture of the bilateral protection between all the WTO members. This approach allowed us to consider all the economic interactions that exist between the North African countries and the European Union as well as the economic interaction between the North African countries themselves. In addition a special emphasis was given to the compute methods used to aggregate tariffs. Indeed, existing methods of aggregation are underestimating the level of tariffs applied by the European Union on agricultural products. This underestimation induces an underestimation of the effects of agriculture liberalization on North African economies. In this paper, we develop an original method of aggregation that attempts to deal with this problem and that gives a more accurate approximation of the market access barriers applied by the European countries. Our main contribution in this article is to develop an original approach of aggregation that aims to obtain a more realistic estimation of the tariffs faced by developing countries and by consequence to obtain a more realistic estimation of the economic impacts of agricultural liberalization between developed and developing countries.